"Human-made pollution is a large and complex problem that has harmful effects on communities and ecosystems. Understanding these impacts is essential, but it can be daunting when many types of chemical pollution are difficult to conceptualize, especially for elementary school students.
Something every student can understand, however, is trash. Students have seen plastic, glass, paper, and metal litter items along roadsides, falling out of trash cans, and in rivers. There is also a growing social awareness of this litter worldwide. Slogans like “Reduce your Use” and bans and taxes on single-use plastic items are becoming more common. These actions have followed research and stark imagery of animals eating or becoming entangled in trash. Since trash is a concrete example of pollution, something that students can easily see and relate to, it is an excellent starting point to learn about pollution of any kind."
-- from: Talking Trash: A human problem with human solutions (2020), On how early learning about trash pollution was a gateway for students to start thinking about how to reduce their environmental impact